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用HDF型氟电极测定磷矿、磷肥中的氟含量,可用碱分解—盐酸酸化的溶液进行测定(剩余试液可作其它成份的分析)。为抵消熔剂对电极电位的影响,标准中加入与试液相当的熔剂空白溶液。维持最终溶液中的氟离子浓度在10~(-4)—10~(-3)M之间,并在PH6的0.4M柠檬酸钠介质中进行测定,0—4毫克的三氧化二铝对测定无显著干扰。磷矿、磷肥中的其它杂质对氟的测定影响均甚微,故可不进行蒸馏分离直接测定。 EDTA和DCTA可能与铝、氟生成多元络合物而影响柠檬酸钠掩蔽铝的效率,在含铝大于1%的试液中,宜单独使用柠檬酸钠作掩蔽剂而不加入EDTA或DCTA。电极法较原蒸馏法简便快速,分析结果与蒸馏法相符。
Determination of fluorine content in phosphate rock and phosphorus fertilizer by using HDF type fluorine electrode can be measured by alkali decomposition - hydrochloric acid acidification solution (remaining solution can be used for other components analysis). In order to counteract the influence of flux on the electrode potential, add a flux blank solution equivalent to the test solution in the standard. The fluoride concentration in the final solution was maintained between 10 -4 and -10 -3 M and was determined in 0.4 M sodium citrate pH 6, 0-4 mg of aluminum trioxide No significant interference measured. Other impurities in phosphate rock and phosphate fertilizer have little effect on the determination of fluorine, so they can be directly measured without distillation separation. EDTA and DCTA may form multiple complexes with aluminum and fluorine to affect the efficiency of masking aluminum by sodium citrate. Sodium citrate should be used as a masking agent alone in EDTA-free or DCTA-containing solutions containing more than 1% aluminum. The electrode method is simpler and faster than the original distillation method, the analysis result is consistent with the distillation method.